Second-century CE (common era) household pottery sherds found in the city of Napoca (present day Cluj-Napoca, Romania) in Roman Dacia were investigated by polarized light optical microscopy, X-ray powder diffraction, Fourier-transform infrared spectroscopy and cold field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy to obtain information on technology, raw materials and site of production. Compositionally, all samples are similar with comparable fine and semi-fine microstructures and oriented microtextures. Optically, there is a gradual transition from microcrystalline to an amorphous illitic-muscovitic matrix. The small aplastic inclusions are mostly quartz and feldspar. Fine-grained carbonate aggregates are distributed inhomogeneously in the ceramic body. Well-preserved Middle Miocene foraminifera tests are characteristic of the ceramics. The gradual thermal changes of the matrix and the newly formed phases upon firing, such as ‘ceramic melilite’, Fe-gehlenite, clinopyroxene, glass, hematite and some maghemite support inferences regarding the technological constraints in producing the pottery. The firing took place in a mostly oxidizing atmosphere and the temperature extended from at least 850°C to >900°C. The Middle Miocene marly clay from the area surrounding the site shows similar mineralogical and micropalaeontological contents to those of the ceramic specimens and is the best candidate for the raw material used for local production of the Roman pottery.

Twenty frescoes from “The Assumption” Cathedral located in the island town of Sviyazhsk (Tatarstan Republic, Russian Federation)—dated back to the times of Tsar Ivan IV “the Terrible”—were chemically analyzed in situ with a portable X-ray fluorescence (pXRF) spectrometer. The investigation focused on identifying the pigments and their combinations in the paint recipes. One hundred ninety-three micropoints randomly chosen from the white, yellow, orange, pink, brown, red, grey, black, green, and blue areas were measured for major and minor elements. The compositional types separated within each color indicate different recipes. The statistical processing of the data unveiled the most important oxides (CaO, MgO, Fe₂O₃, PbO, SO₃, Sb₂O₃, Al₂O₃, SiO₂, and P₂O₅) and their relationships. The results allowed to infer the mineral composition of the paints, and, hence, the recipes used by the Russian artisans. Slaked lime and slaked dolomitic lime mixed with variable amounts of “antimony white” and “bone white” were used for white, pink, yellow, and orange paints and for preparing a basic batch for all other colors. Mostly yellow ochre, red ochre, and lead minerals, and occasionally blue ochre, green earth, realgar, orpiment, bone black, galena, stibnite, and magnetite were the pigments involved in various amounts in preparing the paints.

A Miocene carbonatic clay quarried in Transylvania (Romania) has been used for more than 100 years for the production of traditional ceramic ware, bricks, and tiles. To investigate the mineralogical and microstructural changes of this clay when heated between 700 °C and 1200 °C, a combination of polarized light optical microscopy, X-ray powder diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectrometry, and Fourier transform infrared spectroscopy was applied. Primary mineral phases such as illite, muscovite, feldspar, carbonate, Fe oxyhydroxides, and quartz undergo a gradual thermal alteration and form, besides a glassy phase, a wide range of minerals such as gehlenite, clinopyroxene, feldspar, maghemite, hematite, mullite, and α-cristobalite. These firing phases can be regarded as ‘ceramic markers’. A comparison between the data obtained by several methods is discussed. The combination of the optical appearance and the microstructure on one side, and the specific associations of primary phases and ceramic markers on the other side, can be used as a ‘ceramic thermometer’ in estimating the firing temperature for ancient ceramics.